1. Field of the Invention
The present invention relates generally to virology and disease control. Specifically, the present invention relates to mutated arthropod vectored viruses and their uses as vaccines.
2. Description of the Related Art
Arthropod vectored viruses (Arboviruses) are viral agents which are transmitted in nature by blood sucking insects. Many of these viruses have membrane bilayers with associated integral membrane proteins which make up the protective envelope of the virus particle (Togaviruses) (Schlesinger, S. and M. J. Schlesinger, 1990).
Collectively, the arthropod vectored viruses are second only to malaria as a source of insect-transmitted disease and death in man and animals throughout the world (Berge A. O. 1975). Among these viral agents are Eastern, Western, and Venezuelan Equine Encephalitis Viruses, Dengue Fever, Japanese Encephalititis, San Angelo Fever, West Nile Fever and Yellow Fever. Further, diseases caused by these agents are in resurgence in North America (NIAID Report of the Task Force on Microbiology and Infectious Diseases 1992, NIH Publication No. 92-3320) as a result of the introduction of the mosquito vector Aedes albopictus (Sprenger, and Wuithiranyagool 1985).
By their very nature, Arboviruses must be able to replicate in the tissues of both the invertebrate insect and the mammalian host (Brown, D. T., and L. Condreay, 1986, Bowers et al. 1995). Differences in the genetic and biochemical environment of these two host cell systems provide a basis for the production of viruses which can replicate in one host but not the other (Host Range Mutants).
Currently, Dengue Fever and Eastern Equine Encephalitis and other insect bourne viruses are in resurgence in the United States. The U.S. Army and other government agencies have been trying to make vaccines against these viruses since the 1960s with little success. Thus, the prior art is deficient in a vaccine against most arthropod vectored viruses and other membrane-coated viruses. The present invention fulfills this long-standing need and desire in the art.
In one embodiment of the present invention, there is provided a genetically engineered, membrane-enveloped virus, wherein the virus codes for a transmembrane protein which has a deletion of one or more amino acids such that the transmembrane protein is able to span or correctly integrate into the viral membrane when the engineered virus replicates in insect cells, but is unable to span or correctly integrate into the viral membrane when the virus replicates in mammalian cells. Preferably, the virus is an Arthropod vectored virus selected from the group consisting of Togaviruses, Flaviviruses, Bunya viruses and all other enveloped viruses which can replicate naturally in both mammalian and insect cells, as well a s other enveloped viruses which can be made to replicate in mammalian and insect cells by genetic engineering of either the virus or the cell. Representative examples of such engineered viruses are xcex94K391 virus and TM16 virus.
In another embodiment of the present invention, there is provided a method of producing a viral vaccine from a genetically engineered, membrane-enveloped virus for vaccination of mammals, comprising the steps of producing deletions in the membrane associated domains of the virus which restrict their ability to grow to insect cells, introducing the engineered virus disclosed herein into insect cells and allowing the virus to replicate in the insect cells to produce a viral vaccine. Representative examples of the engineered viruses are xcex94K391 virus and TM16 virus.
In still another embodiment of the present invention, there is provided a method for vaccinating an individual in need of such treatment comprising the step of introducing the viral vaccine of the present invention into the individual to produce viral proteins for immune surveillance and stimulate immune system for antibody production.
In still yet another embodiment of the present invention, there is provided a method of producing a viral vaccine from a genetically engineered, membrane-enveloped virus to a disease spread by a wild mosquito population to mammals, comprising the steps of engineering a deletion of one or more amino acids in a viral transmembrane protein to produce an engineered virus, similar to TM16 or delta K391, wherein the transmembrane protein is able to span the membrane envelope when the virus replicates in mosquito cells, but is unable to span the membrane envelope when the virus replicates in mammalian cells, and wherein the virus remains capable of replicating in wild mosquito cells; introducing the engineered virus into the wild mosquito population; and allowing the engineered virus to replicate in cells of the wild mosquito population to produce a population of mosquitoes which harbor the vaccine strain of the virus and exclude the wild type (pathogenic) virus such that the mosquito bite delivers the vaccine to a mammal bitten. Presence of the mutated virus renders the mosquito incapable of transmitting other membrane containing viruses (Karpf et al 1997)
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of one of the presently preferred embodiments of the invention. These embodiments are given for the purpose of disclosure.